As shown in FIG. 1, a memory cell 100 of a magnetic random access memory (MRAM) has a structure such that a magneto resistive effect element 101 and a select transistor 102 are electrically connected in series. Source, drain, and gate electrodes of the select transistor 102 are electrically connected to a source line 103, a bit line 104 via the magneto resistive effect element 101, and a word line 105, respectively. The magneto resistive effect element 101 has a three-layer structure as a basic structure in which a non-magnetic layer 108 is sandwiched between two ferromagnetic layers, i.e., a first ferromagnetic layer 106 and a second ferromagnetic layer 107. In the illustrated example, the first ferromagnetic layer 106 has a fixed magnetization direction and provides a pinned layer. The second ferromagnetic layer 107 has a variable magnetization direction and provides a recording layer. The magneto resistive effect element 101 has a low resistance when the magnetization direction of the first ferromagnetic layer 106 and the magnetization direction of the second ferromagnetic layer 107 are parallel to each other (P state), or a high resistance when the directions are anti-parallel to each other (AP state). In the MRAM, the changes in resistance are associated with bit information of “0” and “1”. The bit information is written by spin-torque-induced magnetization reversal due to a current that flows through the magneto resistive effect element 101. When the current flows from the pinned layer to the recording layer, the magnetization of the recording layer is anti-parallel to the magnetization of the pinned layer, and the bit information is “1”. When the current flows from the recording layer to the pinned layer, the magnetization of the recording layer is parallel to the magnetization of the pinned layer, and the bit information is “0”. Because the speed of magnetization reversal by the current is on the order of one nanosecond, the MRAM is capable of writing at very high speed. Further, because the recording of bit information is based on the direction of magnetization of the recording layer, the MRAM is non-volatile and can reduce power consumption during standby. Thus, the MRAM is gaining attention as a next-generation memory.
While FIG. 1 shows the case in which, in the magneto resistive effect element 101, the first ferromagnetic layer 106 is the pinned layer and the second ferromagnetic layer 107 is the recording layer, a similar MRAM operation can be performed when the first ferromagnetic layer 106 is configured as the recording layer with a variable magnetization direction and the second ferromagnetic layer 107 is configured as the pinned layer with a fixed magnetization direction. In this case, too, the magnetization of the recording layer is anti-parallel to the magnetization of the pinned layer when a current flows from the pinned layer to the recording layer, such that the bit information is “1”. When the current flows from the recording layer to the pinned layer, the magnetization of the recording layer is parallel to the magnetization of the pinned layer, and the bit information is “0”.